System and method for startup of a power production plant

Abstract

The present disclosure relates to systems and methods that provide power generation using predominantly CO2 as a working fluid. In particular, the present disclosure provides for particular configurations for startup of a power generation system whereby the combustor may be ignited before the turbine is functioning at a sufficiently high speed to drive the compressor on a common shaft to conditions whereby a recycle CO2 stream may be provided to the combustor at a sufficient flow volume and flow pressure. In some embodiments, a bypass line may be utilized to provide additional oxidant in place of the recycle CO2 stream.

The invention claimed is: 
     
       1. A power production system comprising:
 a combustor; 
 a turbine that includes a gland seal and an air input; 
 a first compressor that is a shaft-driven compressor driven by the turbine; 
 an oxidant compressor; 
 an exhaust flow line configured for passage of a turbine exhaust stream from the turbine to the first compressor; 
 a recycle flow line configured for passage of a CO 2  recycle stream from the first compressor to the combustor; 
 an oxidant flow line configured for passage of an oxidant stream from the oxidant compressor to the combustor; 
 a bypass line configured for passage of at least a portion of the oxidant stream from the oxidant flow line to the recycle flow line; 
 a gland seal compressor configured to receive and compress a stream of air and turbine exhaust from the gland seal; 
 a vent in arrangement with the gland seal compressor to receive a flow from the gland seal compressor: and 
 a vent line between the gland seal compressor and the vent. 
 
     
     
       2. The power production system according to  claim 1 , wherein the bypass line includes a valve. 
     
     
       3. The power production system according to  claim 2 , wherein the bypass line valve is configured to be open below a first turbine threshold speed. 
     
     
       4. The power production system according to  claim 2 , wherein the bypass line valve is configured to be closed above a second turbine threshold speed. 
     
     
       5. The power production system according to  claim 1 , further comprising a recuperative heat exchanger. 
     
     
       6. The power production system according to  claim 5 , wherein the exhaust flow line, the recycle flow line, and the oxidant flow line are configured for passage of their respective streams through the recuperative heat exchanger. 
     
     
       7. The power production system according to  claim 1 , wherein the oxidant compressor is a motor-driven compressor. 
     
     
       8. The power production system according to  claim 1 , wherein the vent line between the gland seal compressor and the vent is in a flow arrangement with the exhaust flow line, and wherein the vent line and the exhaust flow line are arranged relative to the vent for preferential flow to the vent from the respective lines. 
     
     
       9. A method for startup of a power production plant, the method comprising:
 pressurizing an oxidant stream in a motor-driven oxidant compressor; 
 passing pressurized oxidant from the oxidant compressor to a combustor through an oxidant flow line; 
 combusting a fuel with the oxidant in the combustor; 
 expanding a combustion product stream from the combustor in a turbine; 
 cooling a turbine exhaust stream from the turbine in a recuperative heat exchanger; 
 removing water from the turbine exhaust stream to form a CO 2  recycle stream; and 
 compressing the CO 2  recycle stream in a shaft-driven compressor driven by the turbine to form a compressed CO 2  recycle stream configured for passage to the combustor in a recycle flow line passing through the recuperative heat exchanger; 
 wherein the compressed CO 2  recycle stream is recirculated and oxidant from the motor-driven oxidant compressor is passed through the recycle flow line to the combustor until the turbine reaches a defined threshold speed that is 50% of the normal operation speed. 
 
     
     
       10. The method according to  claim 9 , wherein the defined threshold speed is 85% of the normal operation speed. 
     
     
       11. The method according to  claim 9 , wherein the oxidant entering the oxidant compressor is a mixture of O 2  and CO 2 . 
     
     
       12. The method according to  claim 9 , wherein the oxidant entering the oxidant compressor is air. 
     
     
       13. The method according to  claim 12 , wherein the turbine includes a gland seal, an air input, and a gland seal compressor configured to receive and compress a stream of air and turbine exhaust from the gland seal. 
     
     
       14. The method according to  claim 9 , wherein substantially none of the compressed CO 2  recycle stream is passed to the combustor through the recycle flow line until the turbine reaches the defined threshold speed.